Electrically tunable liquid crystal lens set with central electrode
A liquid crystal lens cell set includes a plurality of liquid crystal lenses overlapping to each other. Each of the liquid crystal lenses is supported between a pair of flat layers. One of the layers supports a planar electrode made of ITO. The other electrode, also formed of ITO, is supported in the center of the opposing substrate and projects toward the center of the liquid crystal layer. A power supply creates a potential difference between the electrodes and imposes a non-uniform electric field on the liquid crystal modules which aligns them in which a way as to act as a lens. By varying voltage between the electrodes the focal length of the lens may be controlled. A central electrode may be in the form of a beam or of a pointed tip. An electrode having a central hole may be associated with the central electrode or the planar electrode.
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This application is a continuation in part of U.S. application Ser. No. 12/396,613 filed on Mar. 3, 2009, which claims the benefit of U.S. Provisional application Ser. No. 61/033,050 filed on Mar. 3, 2008, both of which are incorporated herein entirely by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates to liquid crystal cells sandwiched between electrodes which exert a non-uniform field on the liquid crystals so as to cause them to act as lenses, and more particularly to such a cell in which the voltage between the electrodes may be varied to control the focal length of the lens and a liquid crystal lens set including a plurality of the cells stacked each other.
2. Description of the Prior Art
Electrically tunable liquid crystal lenses potentially provide important advantages of size and cost over mechanical zoom lenses. They might be used in cameras, binoculars and other opto-electronic devices.
Broadly, these devices employ a pair of electrodes sandwiching a liquid crystal cell. The electrodes are such as to align the liquid crystal molecules to provide a gradient refractive index profile on the lens, transverse to the light path. By use of a variable power supply to adjust the voltage between the electrodes, the focal lengths of the lenses can be varied between a very short focal length and to near infinity, One method proposed to generate a nonhomogeneous electric field within the LC layer is to provide one of the electrodes in spherical shape. Another proposal is to place a central hole in one of the electrodes so as to impose a nonhomogeneous across the LC element.
SUMMARY OF THE INVENTIONThe present invention comprises an electrically tunable LC lens set including a plurality of liquid crystal lenses overlapping to each other along a vertical projective direction. Each of the liquid crystal lenses embodies an LC layer sandwiched between two planar nonconductive layers. One of the nonconductive layers is coated with an ITO (indium tin oxide) layer which acts as a transparent electrode. The other nonconductive layer is formed with a central electrode that projects toward the LC layer and the other electrode. The LC layer, the central electrode, and the other electrode are stacked along the vertical projective direction. The central electrode may take the form of a thin rod with its axis aligned normally to the LC layer or an electrode with a pointed tip terminating close to the LC layer. Either form of electrode may be connected to a power supply at the other end by either a conductive transparent ITO coating extending over an insulation layer or a single transparent conductor formed on the side of the insulation layer opposite to the LC layer. The insulation layer separates this conductive layer from the electrode tip so that the electric field imposed on the LC layer is primarily a function of the voltage between the central tip and the electrode layer on the opposite side of the LC layer.
The resulting nonhomogeneous field aligns the LC molecules so as to produce a refractive index gradient over the LC layer which causes it to act as a lens. By varying the voltage between the tipped electrode and the opposed flat electrode, the focal length of the resulting lens may be controlled.
This unique electrode structure can be combined with an ITO layer having a central hole which is substantially larger than the tip electrode diameter. This electrode could be formed on the opposite side of the insulation layer from which the tip electrode projects or it could constitute the opposing electrode on the opposite side of the LC layer. A high resistance material layer may be formed in the central hole.
The birefringency problem caused by liquid crystal material can be resolved either by use of two layers of liquid crystal aligned in orthogonal directions or through the use of a tin layer of polarizer film attached on top of the LC layer.
In the electrically tunable LC lens set of the present invention, two adjacent liquid crystal lenses may constitute identical or opposite lens effects for forming a required optical performance of the LC lens set.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Other objects, advantages and applications of the present invention will be made apparent by the following detailed description of preferred embodiments of the invention. The description makes reference to the accompanying drawings in which:
Referring to the drawings,
The two ITO layers are connected to a variable voltage power supply 20. By varying the voltage on the two ITO electrodes, a field is imposed on the LC layer which causes the LC molecules to align and produce a lens-like refraction of light passing through the cell. By adjusting the strength of the field the alignment may be varied to modify the focal length of the lens.
The central projecting tip 26 of the ITO layer 24 results in a more intense field being opposed in the center of the LC layer, compared to its edges, so as to give a lens-like curvature to the refractive index of the LC layer. This produces a lens-like effect when incident light passes through the cell.
In another embodiment of the invention illustrated in
It is worth noting that the liquid crystal lenses 110 overlap to each other along the vertical projective direction Z. In this embodiment, the electrically tunable liquid crystal lens set 100 includes a liquid crystal lens 110A and a liquid crystal lens 110B. The liquid crystal lens 110A overlaps the liquid crystal lens 110B along the vertical projective direction Z. The lens effect of the liquid crystal lens 110A may be identical or opposite to the lens effect of the liquid crystal lens 110B. For example, the liquid crystal lens 110A and the liquid crystal lens 110B may respectively institute a convex lens effect or a concave lens effect, but the present invention is not limited thereto. Each of the liquid crystal lenses may be used to form other appropriate lens effects and the electrically tunable liquid crystal lens set 100 may include more than two liquid crystal lenses 110 for other design considerations.
In this embodiment, the electrically tunable liquid crystal lens set 100 may further include a plurality of glass substrates 114 stacked along the vertical projective direction Z. Two adjacent glass substrates 114 are disposed in contact with the first electrode 116 and the second electrode 124 on the sides of the first electrode 116 and the second electrode 124 opposed to the liquid crystal layer 112. In this embodiment, the second electrode 124 of the liquid crystal lens 110A may be disposed on one of the glass substrate 114 on the side opposite to the second electrode 124 of the liquid crystal lens 110B for forming specific optical effects, but not limited thereto.
Additionally, each of the liquid crystal lenses 110 in this preferred embodiment of the invention differs from the prior art in the structure of one of the ITO layers 122 and in the provision of an insulation layer 128. The ITO layer 122 is formed on the side of one of the glass substrates 114 that opposes the liquid crystal layer 112. The second electrode 124 comprises the ITO layer 122 and the central tip electrode 126 that projects from the surface of the ITO layer 122 toward the LC layer 112. In other words, the ITO layer 122 may be regarded as a layer extending over the entire liquid crystal layer 112 and the central tip electrode 126 may be regarded as an extension section supported at a center of the second electrode 124. The second alignment layer 118B is formed beyond the edge of the central tip electrode 126 so as to be proximate to the LC layer 112. The space between the ITO layer 122 and the second alignment layer 118B is coated with the insulation layer 128. The insulation layer 128 must be electrically insulating and transparent. Preferably SiO2 or SiOx may be employed. The insulation layer 128 may surround a central section in abutment to the second alignment layer 118B. In addition, the central tip electrode 126 in the liquid crystal lens 110 may preferably extend in a direction opposite to the neighbor liquid crystal lens 110. As shown in
The central tip electrode 126 of the second electrode 124 results in a more intense field being opposed in the center of the LC layer 112, compared to its edges, so as to give a lens-like curvature to the refractive index of the LC layer 112. This produces a lens-like effect when incident light passes through the cell. The fringe pattern produced by the central tip electrode 126 in this embodiment is similar to the fringe pattern shown in
An alternative form of insulation layer and ITO layer in this embodiment may also be referred to
To summarize the above descriptions, in the electrically tunable liquid crystal lens set of the present invention, the central tip electrode in each liquid crystal lens is used to impose a nonhomogeneous electric field on the liquid crystal layer. The liquid crystal lenses are disposed in a stacked configuration and two adjacent liquid crystal lenses may constitute identical or opposite lens effects for generating different optical effects.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Claims
1. An electrically tunable liquid crystal lens set comprising:
- a plurality of liquid crystal lenses, each of the liquid crystal lenses comprising: a planar liquid crystal layer supported between an opposed pair of transparent, insulating, alignment layers; a first planar electrode formed of a transparent conductive material supported adjacent to one of the alignment layers on the opposite side of the liquid crystal layer; a second transparent conductive electrode disposed on the second alignment layer on the side opposite to the liquid crystal layer, the second electrode comprising only one central tip electrode, wherein the liquid crystal layer, the first electrode, and the second electrode are stacked along a vertical projective direction; and a variable voltage power supply connected to the first and second electrodes so as to impose a nonhomogeneous electric field on the liquid crystal layer, the field having a maximum intensity at a center of the electrodes and decreasing toward the edges of the electrodes, so that the refractive index of the liquid crystal layer is adjusted in a nonhomogeneous manner to provide a lens effect to light passing through the liquid crystal lens, the focal length of the lens being a function of the applied voltage between the first and the second electrodes;
- wherein the liquid crystal lenses overlap to each other along the vertical projective direction.
2. The liquid crystal lens set of claim 1, wherein at least one of the liquid crystal lenses comprises a transparent insulation layer surrounding a central section in abutment to the alignment layer.
3. The liquid crystal lens set of claim 1, further including a plurality of glass substrates, wherein two adjacent glass substrates are disposed in contact with the first and second electrodes.
4. The liquid crystal lens set of claim 3, wherein two adjacent glass substrates are disposed on the sides of the first and second electrodes opposed to the liquid crystal layer.
5. The liquid crystal lens set of claim 3, wherein at least one of the glass substrates is disposed between the first electrode and the liquid crystal layer.
6. The liquid crystal lens set of claim 1, wherein the second electrode further comprises a layer extending over the entire liquid crystal layer and having an extension section supported at a center of the second electrode.
7. The liquid crystal lens set of claim 1, wherein at least one of the liquid crystal lenses further comprises a transparent conductive element connecting a central extension section to one terminal of the power supply.
8. The liquid crystal lens set of claim 1, wherein the only one central tip electrode varies in width from a small tip at an end nearest to the liquid crystal layer to a larger diameter at an opposite end.
9. The liquid crystal lens set of claim 1, wherein the first electrode has a central hole therein.
10. The liquid crystal lens set of claim 3, wherein at least one of the liquid crystal lenses further comprises a third electrode having a central hole therein and disposed between one of the alignment layers and the glass substrate which supports the second electrode, with the only one central tip electrode extending centrally through the central hole in the third electrode; and a separate variable voltage power supply operative to vary the voltage between the third electrode and the first electrode.
11. The liquid crystal lens set of claim 10, wherein at least one of the liquid crystal lenses comprises a high resistance material layer disposed in the central hole of the third electrode.
12. The liquid crystal lens set of claim 1, wherein the transparent conductive electrodes constitute indium tin oxide.
13. The liquid crystal lens set of claim 1, wherein the central tip electrode extends in a direction opposite to the neighbor liquid crystal lens.
14. The liquid crystal lens set of claim 1, wherein the central tip electrode extends in a direction toward the neighbor liquid crystal lens.
15. A liquid crystal cell constituting electrically controllable focal length lenses, comprising:
- a plurality of glass substrates stacked along a vertical projective direction; and
- a plurality of liquid crystal lenses, each of the liquid crystal lenses comprising: a liquid crystal layer sandwiched between first and second planar insulating transparent alignment layers; a first transparent conductive electrode coated on a surface of the first alignment layer opposed to the liquid crystal layer and extending over the full width of the first alignment layer; a second conductive transparent electrode supported on the side of the second alignment layer opposed to the liquid crystal layer, the second electrode having only one central tip electrode, wherein the liquid crystal layer, the first electrode, and the second electrode are stacked along the vertical projective direction; a transparent insulation layer disposed in contact with the side of the second alignment layer opposite to the liquid crystal layer and surrounding a projecting section of the second electrode; and a variable voltage power supply connected to the first and second electrodes and operative to impose a nonhomogeneous electric field on the liquid crystal layer, the voltage of the power supply determining the focal length of the resulting lens, wherein the liquid crystal lenses overlap to each other along the vertical projective direction, and two adjacent glass substrates are disposed in contact with the first and second electrodes on their sides opposite to the liquid crystal layer.
8228472 | July 24, 2012 | Tseng et al. |
20060164593 | July 27, 2006 | Peyghambarian |
20110205342 | August 25, 2011 | Lin |
Type: Grant
Filed: Jun 22, 2012
Date of Patent: May 28, 2013
Patent Publication Number: 20120262663
Assignee: Silicon Touch Technology Inc. (Science-Based Industrial Park, Hsin-Chu)
Inventors: Chi-Yuan Chin (Taipei), Kuei-Jyun Chen (Taoyuan County), Yong Cao (Fujian), Rong-Li Liu (Fujian), Geng Zhong (Sichuan), Zheng Xu (Hangzhou), Ling-Yuan Tseng (Saratoga, CA)
Primary Examiner: Sarah Hahm
Application Number: 13/530,128
International Classification: G02F 1/1337 (20060101); G02F 1/13 (20060101);